Class-S radio frequency (RF) power amplifiers use single-bit sequences to synthesize radio frequency signals. As Class-S technology moves the digital-to-analog boundary towards the power amplifier output stage, an increase in integration relative to analog RF signal processing techniques is made possible. Class-S power amplifiers refer to those amplifiers that filter an applied bitstream, which encodes a desired modulated RF signal, to deliver the bitstream in high-power analog form.
Bitstream generators used in Class-S based RF transmitters upshift baseband information to a desired carrier frequency while shaping single-bit quantization noise power away from a carrier frequency, FCARRIER. In Class-S power amplifiers associated with the popular 2.14 gigahertz (GHz) cellular band, the output stage of the amplifier is switched at a rate in excess of eight (8) billion transitions per second. High-power gallium nitride (GaN) RF transistors have difficulty toggling at this rate, and thus an alternative capable of exploiting transistors having sufficiently fast switching speed would be highly advantageous.